This invention relates to a photosensitive member with a transparent protective resin layer formed on a photoconductive layer formed over an electrically conductive substrate.
As to a conventional photosensitive member used in a copier for electrophotography, the one which has a photoconductive layer formed on an electrically conductive substrate as an image-forming surface, is generally used. When such a photosensitive member is used repeatedly for a long time, there arises such a trouble that the properties of photoconductive layer are deteriorated because of various influences on the surface of the photosensitive member. For example, when the surface of a photoconductive layer is charged repeatedly for a long time with a corona-charger etc. in order to charge a photoconductive member, there arises such a trouble that image qualities are deteriorated because of gradual oxidation by ozone on the surface of the photoconductive layer.
On the other hand, residual toners adhered to the surface of a photoconductive layer are removed by rubbing the surface of the photoconductive layer with a brush or a blade cleaner. The repetition of rubbing brings about such a trouble that the surface of a photoconductive layer is damaged or a photoconductive layer is shaved gradually to get thin. In particular, a blade cleaner which presses the surface of a photoconductive layer causes the so called "filming phenomenon" that toners are buried in the photoconductive layer. Accordingly the life of a photosensitive member is shortened much more.
There is also such a trouble that the properties of a photoconductive layer are much deteriorated by influences of humidity changes.
Therefore, a transparent protective layer is formed on a conventional photoconductive layer in order to protect the photoconductive layer. Needless to say, the transparent protective layer is gradually shaved by a cleaner as above mentioned. Accordingly, it is preferable that the transparent protective layer is as thick as possible so that the photoconductive layer may not be affected adversely as above mentioned.
But, the thicker the transparent protective layer is, the more the residual potential of a photosensitive member increases and fogs in copied images are generated. The reason for the trouble is that the transparent protective layer itself is usually made of resin and has a high electrical volume resistance.
Therefore, the electrical volume resistance of a protective layer was tried to be decreased with various ideas so that the protective layer may be thick without the increase of the residual potential.
Japanese Patent Kokai No. 157748/1980, for example, discloses a protective layer wherein aromatic amine compounds and organic protic acid are dispersed in resin for the formation of the protective layer. These compounds dispersed in the resin, although, are liable not only to be affected by humidity but also to be deteriorated by ozon, and that there is also such a trouble that those compounds can't be contained so much in the resin.
Japanese Patent Kokai No. 30847/1982 discloses a protective layer wherein metal oxide such as zinc oxide and titanium oxide is incorporated in resin for the formation of the protective layer. There was same trouble as above mentioned that this protective layer was liable to be influenced by humidity, ozon and so on.
Further, Japanese Patent Kokai No. 59454/1983 discloses a protective layer comprising ZrO.sub.2, MgF.sub.2, Si.sub.3 N.sub.4 and so on, which is formed on a photoconductive layer by a sputtering method or vapour-depositing method. But, this protective layer is formed in accordance with the shape of the surface of a photoconductive layer. Accordingly, if the surface of the photoconductive layer is uneven, the protective layer becomes irregular. Therefore, there arises such a trouble that toners can't be removed completely by cleaning and linear noises are occurred in copied images because of the poor surface conditions for a photoconductive member.